The present invention relates to a turntable direct-drive system of the type employing a phono-motor having stators placed at the opposite sides of the side wall of a cylindrical rotor.
The turntable direct-drive system in accordance with the present invention may be incorporated in audio recording and/or reproducing systems, especially such as a disk player or magnetic tape recorder.
In the conventional disk players or magnetic tape recorders in which a drive motor is operatively coupled to a turntable through mechanical coupling means such as a belt or idler, wear or deformation of mechanical coupling means causes the fluctuation in rotation of a turntable and adversely affects the performance. To overcome this problem, there has been devised and demonstrated a turntable direct-drive system in which an AC induction motor or DC brushless motor is directly coupled to a turntable shaft. However, a AC induction motor causes vibrations while a DC brushless motor causes the fluctuation in rotational speed of a turntable. Furthermore, a cylindrical rotor is formed integrally with a turntable so that when the turntable is mounted on a turntable shaft, there is a possibility that the shaft and a bearing well for receiving the shaft tend to be subjected to deformations during the shipment. To avoid this problem, the turntable must be detached from the shaft during the shipment. Since the cylindrical rotor which is formed integrally with or attached to the underside of the turntable is very thin, special packing and crating methods must be employed in order to prevent the damage to the cylindrical rotor, thus resulting in the high shipment cost. Furthermore, when the turntable is reassembled by an unskilled user, the thinwall cylindrical rotor tends to be damaged or deformed.